Radial scanner

ABSTRACT

A radial scanning device which provides a moving adjustable slit or window that transverses along an aligned path with respect to a radiation detection device. The repetitive slit motion of the scanning device allows sampling of the liner propellant interface area of a missile motor when the missile is circumferentially rotated.

[4 1 July 8,1975

RADIAL SCANNER Inventors: John W. Mauch, Danville; Emil M.

Bergh, Walnut Creek, both of Calif.

Assignee: The United States of America as represented by the Secretaryof the Navy, Washington, DC.

Filed: Jan. 28, 1974 Appl. No.: 437,441

US. Cl. 250/358; 250/308; 250/321;

250/452; 250/490 Int. Cl. G01t 1/16 Field of Search 250/358, 360, 308,321,

References Cited UNITED STATES PATENTS 2/1934 DeAmicis l78/7.6 6/1950Kaiser ..250/338 Primary ExaminerHarold A. Dixon Attorney, Agent, orFirmR. S. Sciascia; Charles D. B. Curry [57] ABSTRACT A radial scanningdevice which provides a moving adjustable slit or window thattransverses along an aligned path with respect to a radiation detectiondevice. The repetitive slit motion of the scanning device allowssampling of the liner propellant interface area of a missile motor whenthe missile is circumferentially rotated.

5/1932 Jenkins l78/7.6 5 Claims, 11 Drawing Figures RADIATIoN ABSORBER)RAD '3] I33 IAL SCANNER RADIATION ASSEMBLY I BEAM 1 2 newt l STEPPINGI29 65 |29O 5 RADIATION SOURCE MoToR TIA |9 49 I2I I n-f-il 2/ SHELIXSUB-ASSEMBLY 66 DIzTEcToR ASSEMBLY PMET'HEUJUL 8 1975 3.894.234

5g RADIATION H/SCANNER ASSEMBLY 4| DETECTOR ASSEMBLY SUB-ASSEMBLY 66 6|STEPPING 7| MOTOR l9-HEL|cAL SLIT 87 lzucom-zrz FIG 3 SHEET M G-m w wEPATEHTEMUL 8 1975 3.894.234

sum 4 4|\DETECTOR ASSEMBLY 39 l l T 8| l l l I l l 19522545/SCINTILLATION CRYSTAL NETWORK PHOTOMULTIPLIER COLL IMATI N6 95 WINDOW 1 RADIAL SCANNER This application is a co-pending application of thefollowing applications: Ser. No. 270,780 filed July 11, 1972 US. Pat.No. 3,766,387; Ser. No. 270,781 filed July 11, 1972 US. Pat. No.3,803,498; and Ser. No. 328,206 filed Jan. 31, 1973 US. Pat. No.3,832,564.

BACKGROUND OF THE INVENTION 1. Field of the Invention The presentinvention relates to a radial scanner and more particularly a radialscanner which provides a moving slit or window that travels transverslyacross the detecting surface of a radiation detector to sample the linerpropellant interface area of a missile motor.

2. Description of the Prior Art Prior systems have used fixed devicessuch as X-ray systems that record defects on film. This method is veryexpensive because of the high cost of the film. Moreover the X-raytechnique requires tedious repetitive filming sessions to make thenecessary tests to determine the defects in the missile rocket motor.

SUMMARY OF THE INVENTION The present invention relates to a radialscanning device which provides a moving adjustable slit or window thattransverses along an aligned path with respect to a radiation detectiondevice. The repetitive slit motion of the scanning device allowssampling of the liner propellant interface area of a missile motor whenthe missile is circumferentially rotated.

The propellant bond integrity can be determined for each level ofcircumferential scan revolution by the missile motor.

STATEMENT OF THE OBJECTS OF THE INVENTION A primary object of thepresent invention is to provide a radial scanner that will function witha radiation source.

Another object of the present invention is to provide a radial scannerthat is accurate and relatively inexpensive to operate.

Still another object of the present invention is to provide a radialscanner for sampling the liner propellant interface area of a missilemotor or the like.

Other objects advantages and novel features of the invention will becomeapparent from the following detailed description of the invention whenconsidered in conjunction with the accompanying drawings wherein:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a pictorial illustration ofthe radial scanner with its helix system, and the accompanying radiationabsorber.

FIG. 2 is an isometric view of the radial scanner illustrated in FIG. 1.

FIG. 3 is a detailed top cross sectional view of the radial scannerillustrated in FIG. 1, parts being broken away for illustrativepurposes.

FIG. 4 is a cross sectional view of the helix subassembly of the radialscanner including the radiation detector assembly illustrated in FIG. 1.

FIG. 5 is a side sectional view of the left hand section of the helixassembly illustrated in FIG. 4.

FIG. 6 is an end view of the helix assembly of FIG.

FIG. 7 is another side sectional view of the right hand section of thehelix assembly of FIG. 4.

FIG. 8 is a radius section of the longitudinally adjustable assembly ofhelices illustrating the point of contact to form the slit of thehelices illustrated in FIG. 4.

FIG. 9 is the radiation detector to be used with the device illustratedin FIGS. 1 and 2.

FIG. 10 is a side view of the secondary collimating unit illustrated inFIGS. 1 and 3.

FIG. 10A is a side sectional view showing the hollow shaft coupled tothe secondary collimating unit illustrated in FIG. 10.

DESCRIPTION OF THE PREFERRED EMBODIMENT Before describing the radialscanner in detail, it should be noted that the radial scanner may beused with an integrated system such as the radiation detector scannerarrangement described in co-pending patent applications, Ser. No.270,780 and Ser. No. 270,781 both filed on July 11, 1972.

Referring to FIGS. 1 3, the radial scanner assembly 11 comprisesgenerally of a helix sub-assembly 13 which consists of a first cylinder15 and a second cylinder 17 which together forms helical slit 19. Theradial scanner sub-assembly 13 consists of two precisely machinedcylinders, with a minimum density of about 16.76 grams/cc. Firstcylinder 15 is about 6 inches in length while second cylinder is about2% inches in length. Cylinders 15 and 17 may be made of tungsten or itsequivalent. Moreover, the scanner system may be constructed in any sizedesired since size is not generally a controlling factor in the scannerconstruction or function.

Referring to FIGS. 3 8, a 211' helical surface 16 and 18 is machinedinto one end of cylinders 15 and 17 respectively. Precise machining ofthe helical surface may be accomplished by any number of well knownmachine methods.

Referring to FIG. 3, after machining, cylinders 15 and 17 are mountedand supported by a precision ground drive sleeve 21, which is used tocouple the torque from timing pulley 73 to each of the cylinders 15 and17. Drive sleeve 21 may be made of honed stainless steel or itsequivalent. With cylinders 15 and 17 mounted on drive sleeve 21, thedeflection at the center of the sleeve 21 is less than 0.001 inch whenproperly adjusted. Cylinders 15 and 17 are adjustable in thelongitudinal direction and may be locked in position by standardlatching devices. Drive sleeve 21 is formed by a hollow tube, one innersleeve 23 and one outer sleeve 25, machined preferably from stainlesssteel, is bonded to the drive sleeve 21. The bonding material may be ofthe adhesive type or any equivalent bonding material. Referring to FIG.3, outer sleeve 25 also fits into a ball bearing 26 mounted in bearing30 support plate 31 which acts as a guide bearing. Inner sleeve '23 iskeyed to helix end support 29, which is bolted to cylinder 17 androtates inside of large ball bearing which is clamped and mounted inheavy support plate 32. The outsidediameter of this bearing assembly isslightly larger than all the other helix diameters allowing the completehelix sub-assembly 13 to be removed as a unit upon removal of end plate69. Cylinder 15 is bolted to helix end support 27. A splined surface 25ais machined into outer sleeve 25. Moreover, a splined surface ismachined into the inside of helix end support 27. These splined surfacesallow for adjustment of the helix slit 19 width from about 0.000 inchesto about 0.250 inches. Adjustment of the helix slit 19 is made byrotating adjustment nut 33 which is threaded to helix end support 27which is held in place on outer sleeve 25 by retaining ring 35. Afterthe required slit width is obtained, lock nut 37 is snubbed againstrotating adjustment nut 33 to lock cylinder 15 to outer sleeve 25. Thewhole sub-assembly 13 is mounted in the bored section of support plates31 and 32.

Referring to FIGS. 3, 4 and 9 detector holder tube 39 is held stationaryand is used to hold detector assembly 41 which consists of aphotomultiplier tube 43, sodium iodide scintillation crystal 45 andvoltage divider network assembly 47. Detector holder tube 39 and supportshaft 81 are suspended inside of inner sleeve 23 of drive sleeve 21.Detector holder tube 39 is mounted within drive sleeve 21 and positionedso that no contact can occur between drive sleeve 21 and detector holdertube 39 even when cylinders 15 and 17 and drive sleeve 21 are rotating.Support for detector holder tube 39 is provided at one end by supportshaft 81 and end plate 69 which is the essentially closed end 81a and atthe other end by end plate 67 and end plate holder 83. The detector 41is slipped into cylinder 15 from the open end of detector holder tube39. Detector 41 can be easily removed or replaced as illustrated in FIG.3.

Referring to FIGS. 1, 3, 10 and 10A, secondary colli mating window 49 isformed by collimating bars 51, 53, 55 and 57. The collimating bars maybe made of tungsten or an equivalent material. Collimating bars 51, 53,55 and 57 are mounted inside side plate 63 and centered within a hollowshaft assembly. In operation the collimating bars 51, 53, 55 and 57 thusform a secondary collimator window along the axial direction of helicalslit 19. Gamma-ray photons or other radiation which pass through hollowshaft 60 and collimating window 49 are detected by the Sodium IodideCrystal 45 or the equivalent as the helical slit 19 scans across theselected window area. Bars 51 and 53 are adjustable as indicated by thedirectional arrows in FIG. 10 to vary the window area.

Referring to FIGS. 1, 2 and 4 angular rotation of helical slit 19 tofollow the contour of the material to be tested is provided by.gimbaling the entire radial scanner assembly 11 between pillow blockgimbal bearing assemblies 59 and 61. Pillow block gimbal bearingassemblies 59 and 61 are respectively bored to accept hollow shaft 60and solid shaft 87. Gear assembly 85 may be of any type which willprovide the proper drive ratios desired and solid shaft 87 is fixedlyattached to assembly 85. Hollow shaft 60 and solid shaft 87 which areattached to side plates 64 and 66 respectively, provide the pivotsurfaces for pillow block 59 and 61 respectively. Pillow blocks 59 and61 can be mounted to a fixed or movable base B of FIG. 2 as desired;however, the heights of the base centers should be located equidistantabove the base surface for proper alignment.

Referring to FIGS. 1, 2, 3 and 10A pivot point of cylinders 15 and 17 islocated so that a line L passing through the centers C of pillow blocks59 and 61 bore diameters is perpendicular to the axis of cylinders 15and 17, bisects the cylinder diameter d illustrated in FIG. 6, and alsobisects the helix pitch when the slit 19 is completely closed asillustrated in FIG. 8.

The radial scanner assembly 11 is gimbaled and is capable of rotatingthrough any angle between 0, horizontal, and 90 vertical and can bedriven if desired so as to follow the contour of any material to betested.

Referring to FIGS. 1 and 2 angular rotation of the gimbaled radialscanner assembly 11 is provided by a stepping motor 71. A SuperiorElectric 1184008 or the like may be used. A positional readout of theangle is determined by encoder 73. A DECITRAK Model TR- 1 lB2-CCW may beused if desired. Timing pulley 72 is mounted on cylinder 17 end support29 and driven by stepping motor 71A as depicted in FIG. 1. A SuperiorElectric S8400 stepping motor using a 2:l pulley ratio is preferredalthough other equivalent devices may be used. If a 2:1 pulley ratio isselected and stepping motor 71A is rotating at 200 steps/second, thehelical slit 19 rotates at 30 revolutions/minute. Positional readoutinformation for helical slit 19 is provided for by slip gear 75A whichis mounted to pulley 72. Using a 1:1 pulley ratio belt 76 is used todrive a second precision tooth no slip pulley 75 and a shaft to drive,standard 360 helipot 77 and a conventional dual cam switch 79. Thecontinuous rotatable helipot 77 is used to determine the angularposition of the helix and also to provide the horizontal sweep voltagefor controlling or monitoring oscilloscopes. Dual cam switch 79preferably is adjustable to provide a 24 volt mark pulse when thehelical slit 19 angular position is at 0. In addition, other adjustmentson switch 79 provide a 24 volt output when the angular position of thehelix slit is between 60 and 300. This 24 volt output can be used toswitch on during the 60 and 300 and off between 300 and 60 of the helixsub-assembly l3 rotation; see patent applications Ser. No. 270,780 andSer. No. 270,781 described above.

The operation of the radial scanner device 11 will be described in lightof the drawings as follows.

In FIGS. 1, 2 and 3 is illustrated the radiation scanner 11 incombination with a radiation absorber 131 which functions to absorbradiation emitted from source 133 to vary the intensity of radiationbeam 127. The source 133 is mounted in inclosure 135. The radiationsource 133 is further located juxtapositioned with the inside face ofradiation absorber 131. Radiation absorber 131 may be of differenttypes; however, it is preferably of the wedge type which is described ina co-pending patent application. The amount of radiation absorbed byradiation absorber 131 is determined by the degree of rotation of theradiation stepping motor, not shown, but described in co-pending patentapplication Ser. No. 328,206 filed on Jan. 31, 1972. Different types andintensity of radiation sources may be employed; however, it has beenfound that an about 2,000 curie cobalt 60 source is adequate for mostpurposes. The angular position of the detector, helix and sensitivityindicator is or may be determined by an angulation stepping device orthe like.

In FIG. 1 the helix sub-assembly 13 is rotatably mounted on pillow blockgimbal bearings 59 and 61. The helix sub-assembly 13 is driven by helixstepping motor 71A and the sensitivity indicator 129 is positioned by asensitivity indicator stepping motor, not shown. The sensitivityindicator 129 is used for purposes of calibration. The sensitivityindicator may have multiple discrete positions or slots 129a. Thefunction of the sensitivity indicator is described in patent applicationSer. No. 270,780 filed on July ll, I972. Helix stepping motor 71 ismounted adjacent to gimbal 59 and rotates helix sub-assembly 13. Helixsub-assembly 13 is cylindrically shaped with a hollow interior andcontains a helical slit 19 and a detector assembly 41. The helical slit19 may be machined into a hollow thick-walled cylinder of high densitymaterial such as tungsten or its equivalent. The detector assembly 41 isstationary and is mounted on gimbals 59 and 61. The output signal istransmitted by conductor lead 121. The detector assembly 41 ispreferably a photomultiplier tube having a sodium iodide crystaloptically connected to the photomultiplier tube. A voltage detectioncircuit which may be used in conjunction with the photomultiplier tubeis described in patent application Ser. No. 270,781 filed July 11, 1972.Bearings, not shown in FIG. 1, are provided between detector assembly 41and helix subassembly 13 to provide rotatable support for the helix. Thegimbal bearings 59 and 61 are driven by a conventional angulationstepping motor.

The angulation stepping motor 71 will be driven only when it isnecessary to scan the hemispherical dome region of the missile motor orthe like. The operation of the angulation stepping motor 71 may be byuse of a numerical controlled punch tape electric drive which providesoutput pulses to the various motors as dictated by the particular tapethat is being used which is considered conventional and well known tothose skilled in the art and is not considered part of the presentinvention.

Sensitivity indicator 129 may be of any type; however, the most suitablewould be a circular plate made of a radiation absorbing material that isprovided with a plurality of slots 129a of progressively increasingsize. The sensitivity indicator is driven by a stepping motor, not shownin FIG. 1, such that one of the slots 129a is positioned in alignmentwith opening 49. After calibrating the sensitivity, indicator 129 istaken out of the system operation by aligning the largest slot 129a withadjacent collimating window 49 of FIG. 3. The radiation beam 127 passesthrough radiation absorber 131, one of slots 1290, opening 49, helicalslit l9 and impinges upon the surface of detector assembly 41. Thewindow size of the detector, determined by the width and length of slit19, is about 0.050 X 1 inch. The 0.050 is selected because it is largeenough to receive sufficient photon flux to provide an acceptable signalto noise ratio and it is small enough to recognize separation defects ofabout 0.005 inch. That is, if the window were much wider than 0.050inch, then a small defect would have little effect on the detectoroutput signal. The length of 1.00 inch was selected because it is aboutthe diameter of a defect necessary to be detected and is sufficientlylong to provide an adequate inspection time.

What is claimed is:

l. A radial scanning devicefor sampling the interface area integrity ofa member and including a radiation source and comprising:

a. a means for scanning said member;

b. said scanning means comprises a detector;

0. said radiation source emitting radiation for passing through saidmember;

d. said means positioned for scanning radiation passing through saidmember;

e. said detector of said scanning means comprises a cylinder having ahelical slit formed therein;

f. said radiation detector positioned within said cylinder;

g. first means for rotating said cylinder about its longitudinal axis;and

h. second means for rotating said detector and said cylinder about anaxis perpendicular to said longitudinal axis.

2. The device recited in claim 1 wherein:

a. said helical slit is comprised of a first cylinder and a secondcylinder; and

b. each of said cylinders having a cam shaped helical surface.

3. The device recited in claim 2 wherein:

a. said scanner comprises an adjustable moving slitted window alignedwith respect to said helix surface.

4. The device recited in claim 3 wherein:

a. said moving slit comprises afirst movable wall and a second movablewall.

5. The device recited in claim 2 wherein:

a. said cylinders are rotatably mounted on a rotating shaft; and

b. a detector located in alignment with said helical slit, said helicalslit positioned opposite an adjustable window slot for scanningradiation passing through a member.

1. A radial scanning device for sampling the interface area integrity ofa member and including a radiation source and comprising: a. a means forscanning said member; b. said scanning means comprises a detector; c.said radiation source emitting radiation for passing through saidmember; d. said means positioned for scanning radiation passing throughsaid member; e. said detector of said scanning means comprises acylinder having a helical slit formed therein; f. said radiationdetector positioned within said cylinder; g. first means for rotatingsaid cylinder about its longitudinal axis; and h. second means forrotating said detector and said cylinder about an axis perpendicular tosaid longitudinal axis.
 2. The device recited in claim 1 wherein: a.said helical slit is comprised of a first cylinder and a secondcylinder; and b. each of said cylinders having a cam shaped helicalsurface.
 3. The device recited in claim 2 wherein: a. said scannercomprises an adjustable moving slitted window aligned with respect tosaid helix surface.
 4. The device recited in claim 3 wherein: a. saidmoving slit comprises a first movable wall and a second movable wall. 5.The device recited in claim 2 wherein: a. said cylinders are rotatablymounted on a rotating shaft; and b. a detector located in alignment withsaid helical slit, said helical slit positioned opposite an adjustablewindow slot for scanning radiation passing through a member.